Social density refers to the number or concentration of people present within a given physical space or area at a particular time ^[1]. In contrast to spatial density, which concerns the amount of space available to a given number of people, social density changes when the number of people increases or decreases while the physical space remains constant ^[2]. In urban environments, social density can occur in residential areas, public spaces, transportation facilities, commercial areas, and other settings where people share space and interact with one another ^[3]. High social density may increase opportunities for social contact and interaction, but it can also affect perceptions of personal space, privacy, control, and environmental comfort. Its effects are influenced by social relationships, cultural expectations, characteristics of the physical environment, and the activities taking place in the setting. Social density should therefore be distinguished from crowding, which refers to the subjective experience or evaluation of excessive density rather than the physical condition itself.